disappering fish??

So i have or had two maroon clowns and three cardinals in a 65gal tank. Lots of live rick and sand bottom. Then i notice that i only see two cardinals yhinking its just hiding never pay mind to it. Well last week one nite i seen my two clowns and both looked great not fighting and healthy. The next morning one is missing. I finally move rocks around and find it. Its fims are completely tattered and ate off. I imediantly check water and all tests come back in great ranges. So i yhink maybe clowns got in fight and move on. Yesterday i notice only one carifnal amd again think its hiding but am more cautious this time. So im watching and later in yhe eveing fish still missing and i see all theae tiny little worm things awimming and floating around. They are no more than a 1/4in long and pink. I seen about a dozen of them. What are they and could they be attacking my fish? Could my clown be? Everyone seemed to be getting along great. And all fish looked healthy before disappering. Im losing my fish and at a complete loss help!:cry:

Btw worms are not around during day or at least i dont see them.